Capacitive sensing with multi-pattern scan

ABSTRACT

The sensing circuit includes including first input of a first electrode, a first set of inputs of a first set of two or more electrodes forming a first intersection and a second intersection, and a second set of inputs of a second set of two or more electrodes forming the second intersection and a third intersection. The sensing circuit includes a scan control circuit, coupled to the touch panel of electrodes, to concurrently select the sets of electrodes via a multiplexer. The touch sensing circuit includes an analog front end configured to generate digital values representative of mutual capacitances of a first and second unit cell, wherein the first unit cell comprises the first and second intersections and the second unit cell comprises the second and third intersections, and a channel engine configured to generate capacitance values corresponding to the unit cells.

RELATED APPLICATIONS

This patent application claims the benefit of U.S. Provisional PatentApplication No. 62/434,099, filed Dec. 14, 2016, which is incorporatedby reference herein, in its entirety.

TECHNICAL FIELD

This disclosure relates generally to electronic systems, and, moreparticularly, to capacitance sensing and touch detection.

BACKGROUND

Capacitance sensing systems can sense electrical signals generated onelectrodes that reflect changes in capacitance. Such changes incapacitance can indicate a touch event or the presence of ridges andvalleys of a fingerprint. Touch sensing may be used for applications ona variety of user interface devices, such as mobile handsets, personalcomputers, and tablets. The use of capacitance sensing for touchdetection may allow for a touch sensor (also referred to herein as anelectrode, a sensor, etc.) to be placed in or under the surface of auser interface device with a great degree of configurability. In oneembodiment, a touch sensor may not be specific to a single location forall devices. Rather, touch sensors may be disposed where convenient tothe industrial design of the device.

Capacitance-based touch sensors work by measuring the capacitance of acapacitive sense element and sensing a change in capacitance indicatinga presence or absence of an object (e.g., a finger or a ridge or valleyof a fingerprint). When an object comes into contact with, or is inclose proximity to a touch sensor, the capacitance change caused by theobject is detected. The capacitance change of the touch sensor can bemeasured by an electrical circuit and converted into a digitalcapacitance value.

DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings.

FIG. 1 illustrates a system including a touch detection circuit,according to one embodiment.

FIG. 2 illustrates a touch detection circuit, according to oneembodiment.

FIG. 3A illustrates a first multi-pattern scan of a touch detectioncircuit, according to one embodiment.

FIG. 3B illustrates a second multi-pattern scan of a touch detectioncircuit, according to one embodiment.

FIG. 4A illustrates a third multi-pattern scan of a touch detectioncircuit, according to one embodiment.

FIG. 4B illustrates a fourth multi-pattern scan of a touch detectioncircuit, according to one embodiment.

FIG. 5 illustrates a method for multi-pattern scanning, according to oneembodiment.

FIG. 6 illustrates a system including a touch sensor, according to oneembodiment.

FIG. 7 illustrates a method for combining multi-pattern scan images,according to one embodiment.

FIG. 8 illustrates multi-pattern scan images, according to oneembodiment.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the embodiments of the present invention discussedherein. It will be evident, however, to one skilled in the art thatthese and other embodiments may be practiced without these specificdetails. In other instances, well-known circuits, structures, andtechniques are not shown in detail, but rather in a block diagram inorder to avoid unnecessarily obscuring an understanding of thisdescription.

Reference in the description to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. The phrase “in one embodiment” located in variousplaces in this description does not necessarily refer to the sameembodiment.

For simplicity and clarity of illustration, reference numerals may berepeated among the figures to indicate corresponding or analogouselements. Numerous details are set forth to provide an understanding ofthe embodiments described herein. The examples may be practiced withoutthese details. In other instances, well-known methods, procedures, andcomponents are not described in detail to avoid obscuring the examplesdescribed. The description is not to be considered as limited to thescope of the examples described herein.

In one embodiment, capacitive touch sensors detect very small signalsthrough thicker and thicker overlays that may result in signaldegradation. To operate under thick-overlays or support thick gloves andhigh-distance hover detection (e.g., detection of an object hoveringabove the overlay), capacitive systems may benefit from higher signal tonoise ratios. In one embodiment, a single-pixel scan method (driving asingle transmit electrode (TX) and sensing a single receive electrode(RX)) provides cell mutual capacitance (Cm) of a single TX and single RXelectrode intersection. In one embodiment, intersections are formed bythe physical overlay of one electrode over another (e.g., diagonally,perpendicularly, etc.) In one embodiment, in a single-pixel scan, asingle intersection and the surrounding area may be thought of as a unitcell. Single-pixel scans may experience a low signal-to-noise ratio iftouches are to be detected under certain conditions (e.g., under thickglass, through gloves, etc.). As described herein, in anotherembodiment, multiple TX and RX electrodes may be selected (driven andsensed, respectively) concurrently to produce a higher signal to noiseratio by effectively increasing the size of a unit cell to include morethan one intersection. Concurrently selecting grouped (e.g., sets of)electrodes may result in bigger mutual capacitances and bettersensitivity to touch with a scan time that is proportional to that ofsingle-pixel scans. For example, if two TX electrodes and two RXelectrodes are grouped (concurrently selected), the resulting Cm of thelarger unit cell (e.g., including four intersections) may beapproximately four times the Cm of a smaller unit cell of a single TXand RX intersection.

It should be noted that the operations described herein may be equallyapplied to self-capacitance (absolute capacitance) andmutual-capacitance touch detection systems. In one embodiment, in aself-capacitance system an object (e.g., a finger) on a single sensorincreases the parasitic capacitance of the sensor relative to ground. Inanother embodiment, in a mutual capacitance system, the object altersthe mutual capacitive coupling between row and column electrodes (TX andRX electrodes) which may be scanned sequentially.

FIG. 1 illustrates a system 100 with a touch detection circuit 101,touch controller 105, host 112, and device 120. Touch detection circuit101 may include a number of electrodes arranged in an array 102 of rowelectrodes 104 and column electrodes 106, each coupled to a touchcontroller 105. FIG. 1 illustrates eight row electrodes 104 and eightcolumn electrodes 106, but there may be considerably more electrodesdisposed along both axes. Depending on the size of the array, there maybe dozens or hundreds of electrodes for each axis (row and column). Thepitch of row electrodes 104 and column electrodes 106 may be smallenough such that multiple rows or columns may be disposed within a spacebetween ridges of a fingerprint or along a ridge of the fingerprint whena finger is in contact with array 102. The exact size and pitch of theelectrodes may depend on the system design requirements.

Row electrodes 104 and column electrodes 106 may be disposed such that amutual capacitance, C_(MX), is formed between them. A value of C_(MX)may then correspond to each unit cell of array 102. In one embodiment, aunit cell is a capacitance sensor. As applied to capacitance sensors,the repeated pattern of a unit cell may define the resolution of thesensor. Unit cells may correspond to discrete locations on an array ofelectrodes. In one embodiment, every point within a unit cell is closerto the center of the unit cell than any other unit cell. In oneembodiment of multi-pattern scan, unit cells include multipleintersections. For example, a unit cell that includes four intersectionsmay include the intersections formed by two row electrodes 104 and twocolumn electrodes 106.

In the example of FIG. 1, a total of 64 intersections are illustrated.In an array with 75 row electrodes and 125 column electrodes, there maybe 9,375 intersections. Electrodes (columns and rows) with dashed linesindicate that considerably more columns or rows may be disposed alongeither axis. While only eight electrodes (row electrodes 104 and columnelectrodes 106) are illustrated, this is merely for simplicity ofdescription. One of ordinary skill in the art would understand thatcolumns and rows that are dashed represent dozens or even hundreds ofelectrodes. The calculated values of C_(MX) (or digital valuesrepresentative of mutual capacitance C_(MX)) may be used by touchcontroller 105 or a host 112 to detect a touch or the presence of aridge or valley of a fingerprint.

FIG. 2 illustrates a touch detection circuit 200, according to oneembodiment. Sensor grid 201 may be comprised of a plurality of rowelectrodes 202.1-202.N disposed along a first axis and a plurality ofcolumn electrodes 203.1-203.N disposed along a second axis. In oneembodiment, the row and column electrodes may be bar-shaped and disposedon a substrate. A mutual capacitance may exist between each rowelectrode and each column electrode at the intersection between the rowand column. As described above, this mutual capacitance may beconceptualized as a unit cell which can be measured and assigned aspecific identification and capacitance value. Here, row electrodes202.1-202.N and column electrodes 203.1-203.N are shown as simple bars.In other embodiments, they may be composed of more complex shapes, suchas diamonds daisy-chained together to form rows and columns. Rowelectrodes 202.1-202.N and column electrodes 203.1-203.N may includemultiple electrodes coupled together at one end or both ends.

Row electrodes 202.1-202.N may be coupled to RX pins 205.1-205.N andcolumn electrodes 203.1-203.N may be coupled to TX pins 206.1-206.N. RXpins 205.1-205.N and TX pins 206.1-206.N may be part of an integratedcircuit and may be coupled to an RX multiplexer (RX MUX) 211 or to a TXmultiplexor (TX MUX) 212 via multiple channels (e.g., inputs) or thesame channel. RX MUX 211 and TX MUX 212 may be configured to routesignals to and from measurement circuitry to the row and columnelectrodes through the pins. For example, RX MUX 211 and TX MUX 212 maybe configured to concurrently select (e.g., drive to or sense from)multiple (e.g., electrically grouped) electrodes simultaneously. In oneembodiment, RX pins 205.1-205.N may be coupled to analog front end (AFE)220 configured to convert the mutual capacitance between rows andcolumns to at least one digital value. AFE 220 may include a low noiseamplifier (LNA) 240 coupled to row electrodes 202.1-202.N via RX MUX211. In one embodiment, RX MUX 211 may be configured to couple a singlerow electrode to the inputs of LNA 240 at a time. In another embodiment,multiple row electrodes (e.g., RX electrodes) may be coupled to theinputs of LNA 240 (e.g., the inputs of the AFE 220) simultaneously. Instill another embodiment, multiple LNAs may be coupled to RX MUX 211 toallow for individual and simultaneous measurement and the processing ofmultiple capacitances corresponding to multiple RX electrodesconcurrently, each on a different channel of the AFE 220, to produce anoutput for each electrode. In still another embodiment, RX MUX 211 mayinclude several smaller multiplexors, either in parallel or in series,with various input and output configurations. In one embodiment, anon-square sensor matrix may include a different number of RX and TXelectrodes.

In one embodiment, RX MUX 211 may couple RX pins 205.1-205.N to bandpass filter (BPF) to provide a differential input to LNA 240. In oneembodiment, a BPF may remove off-band noise components injected by afinger or other conductive object or originating from other sourcescoupled to different components of a system. In one embodiment, the BPFmay be a passive filter, such as an LC filter. In other embodiments, theBPF may be an active filter, which in certain embodiments may be basedon a gyrator or other active components. In various embodiments, the BPFmay be constructed using external components, integrated into a sensingcircuit with internal circuit elements, or some combination of externalcomponents and internal resources.

The output of the BPF may be coupled to positive and negative inputs ofLNA 240. In one embodiment, the output of the BPF may be coupled toinput pins, thus coupling AFE 220 to an external BPF.

In one embodiment, the output of LNA 240 may be coupled to ademodulation circuit (“demodulator”) 250, which provides an analogsignal to analog-to-digital converter (ADC) 252. Demodulator 250 mayreceive a pair of phase-shifted clocks and demodulate the signal fromthe LNA 240 into two components: I (“in-phase”) and Q (“quadraturephase”). The I and the Q phase may be either differential orsingle-ended, depending on the amplifier implementation.

The I and Q phase may be either differential or single-ended, dependingon the amplifier implementation. The demodulator modifies the inputsignal by multiplying or mixing the pair of quadrature-shifted (0° and90°) demodulator reference signals. A differential input demodulator mayuse a pair of differential quadrature reference phase-shifted signals(0°-180°, 90°-270°) for I and Q channels, respectively.

In one embodiment, the analog signal generated by demodulator 250 isreceived by ADC 252, which may convert the analog signal (voltage) fromdemodulator 250 to a digital value. The output digital value of ADC 252may function as the output of AFE 220. The output of AFE 220 may becoupled to a channel engine 260. Channel engine 260 may include logic tosquare each of the quadrature component outputs of the AFE. Channelengine 260 may include summing logic to combine the squared values ofthe quadrature component outputs of AFE 220. Finally, channel engine 260may include root logic for calculating the square root of the summed,squared quadrature component outputs of AFE 220. The output of channelengine 260 may be a result, R, which may be given by Equation 2:

R=Σ _(n=0) ^(N)(√{square root over (I _(n) ² +Q _(n) ²)}),  (1)

where n is the ADC sample number and N is the total number ofaccumulated ADC samples. The output of channel engine 260 may not dependon the input signal phase, which may eliminate the need for complexcalibration steps.

In various embodiments, channel engine 260 may complete additionalfunctions, including but not limited to calculation of minimum and/ormaximum capacitance values, calculation of minimum and/or maximumcapacitance change values, RMS calculation, and baseline calculation andupdate, offset subtraction, and scaling of accumulated results.

The output (a capacitance value) of channel engine 260 may be passed toa memory, such as a capacitance value storage memory (Cap RAM) 262,which may be part of a CPU interface 270. CPU interface 270 may alsoinclude MMIO registers 266 to program sequencer 255 by CPU interface 270(e.g, setting number of TX pulses per pixel) and a Timer Table memory(Timer Table RAM) 264 to program timing for all sequencer controlsignals (e.g. input tank reset duration prior scanning cycle starts).Timer Table RAM 264 may include an output that is passed to a scancontrol block 280.

Scan control block 280 may include an RX control block 251 and a TXcontrol block 253, both coupled to sequencer 255. Scan control block 280may cause RX MUX 211 and/or TX MUX 212 to electrically couple sets of RXelectrodes, and sets of TX electrodes, respectively. The outputs of RXcontrol block 251 and TX control block 253 may be coupled to RX MUX 211and TX MUX 212, respectively. The control of TX MUX 212 may drive asignal (e.g., a TX signal) to the column electrodes 203.1-203.N (e.g.,drive the TX electrodes). The TX signal may be generated from amplifiers(e.g., drivers) 247 and 249. In one embodiment, amplifiers 247 and 249and TX MUX 212 may be configured to provide a differential TX signal tocolumn electrodes 203.1-203.N. In another embodiment, a single TX signalmay be applied, thus providing a non-differential signal to the columnelectrodes 203.1-203.N.

FIG. 3A illustrates a first multi-pattern scan of a touch detectioncircuit, according to one embodiment. In one embodiment, virtual senseelectrode (e.g., a virtual sense electrode larger than a singleelectrode) may be formed by grouping multiple individual senseelectrodes together dynamically (e.g., groups 306 and 308). Scanning maybe performed by moving the virtual sense electrode across the touchsensing panel, as illustrated. In one embodiment, the resolution (e.g.,pitch) of a scan may be modified by grouping different numbers ofelectrodes together to form a virtual sense electrode and by overlappingor not overlapping electrodes in sequential scans.

FIG. 3B illustrates a second multi-pattern scan of a touch detectioncircuit, according to one embodiment. In one embodiment, scan controlblock 280 enables TX MUX 212 to concurrently drive two or more groupedTX electrodes 302 of a touch panel of electrodes 304 in a first scan. RXMUX 211 may concurrently sense signals from multiple grouped RXelectrodes 308 in response to concurrently driving the TX electrodes.LNA 240, ADC 252 and channel engine 260 may determine a capacitance fora unit cell (e.g., unit cell 310) of the touch panel of electrodes 304,as described above. The unit cell may include multiple intersections(e.g., the four intersections formed by TX electrodes 302 and RXelectrodes 308).

In a second scan, scan control block 280 may enable TX MUX 212 toconcurrently drive a second group of two or more TX electrodes 312 ofthe touch panel of electrodes 304. RX MUX 211 may also concurrentlysense signals from a second group of multiple RX electrodes 314 inresponse to concurrently driving the TX electrodes. LNA 240, ADC 252 andchannel engine 260 may determine a second capacitance for a second unitcell of the touch panel of electrodes 304. The second unit cell mayinclude multiple intersections (e.g., the four intersections formed byTX electrodes 312 and RX electrodes 314). In one embodiment, the outputof channel engine 260 may be sent to a fingerprint controller to detectthe presence of a ridge or a valley of a fingerprint on the touch panelof electrodes 304 based on the capacitance value (e.g., output ofchannel engine 260).

By concurrently driving various groups of TX electrodes and concurrentlysensing signals from various groups of RX electrodes, capacitance valuesfor variously sized unit cells may be determined. The resolution withwhich touch panel of electrodes 304 captures capacitance values maydepend on how many TX electrodes and driven concurrently and how many RXelectrode signals are received concurrently. In various embodiments, thenumber of TX and RX electrodes concurrently selected may be adjusted(e.g., by scan control block 280) to configure the resolution of a scan.In embodiments where a low resolution and fast scanning time may bedesired, more TX and RX electrodes may be selected concurrently (thusincreasing the size of the unit cell). In another embodiment, where ahigh resolution and slower scanning time may be desired, less TX and RXelectrodes may be selected concurrently (thus decreasing the size of theunit cell). In one embodiment, the number of TX electrodes that areconcurrently selected and the number of RX electrodes that areconcurrently selected may be different. In another embodiment the numberof TX electrodes that are concurrently selected and the number of RXelectrodes that are concurrently selected may be the same.

FIG. 4A illustrates a second multi-pattern scan of a touch detectioncircuit, according to one embodiment. As shown in FIG. 4A, a first setof TX electrodes 402 may be driven concurrently and signals from a firstset of RX electrodes 404 may be received concurrently. Capacitancevalues for the four intersections of the TX electrodes 402 and the RXelectrodes 404 may be calculated. In one embodiment, the capacitancevalues may be averaged to determine a capacitance of a unit cell 406that includes the intersections.

In one embodiment, a second scan may be performed by concurrentlydriving a second set of TX electrodes 408 and concurrently receivingsignals from a second set of RC electrodes 410. Capacitance values forthe four intersections of the TX electrodes 408 and the RX electrodes410 may be calculated. In one embodiment, the capacitance values may beaveraged to determine a capacitance of a second unit cell 412 thatincludes the intersections for 408 and 410. In one embodiment, theresolution of the scan depends on the pitch 414 of the unit cells. Thelarger the pitch (e.g., the distance between the centers of unit cells),the larger the unit cells and the lower the resolution of the scan. Inone embodiment, sequential scans may include overlapping electrodes,resulting in smaller unit cells and a slower scan with a highresolution. In another embodiment, scans may skip electrodes (resultingin larger unit cells) to perform a faster scan with lower resolution. Inone embodiment, different numbers of TX and RX electrodes may beactivated concurrently (e.g., two RX electrodes and one TX electrode,two TX electrodes and one RX electrode, one RX electrode and three TXelectrodes, etc.) in various scan modes.

FIG. 4B illustrates a fourth multi-pattern scan of a touch detectioncircuit, according to one embodiment. In one embodiment, variousconfigurations of overlapping scans can provide a different sensorresolution (e.g., which may results in different resulting imageresolutions). For example, in a first scan option 416, a first scan anda second scan may be performed by overlapping a single electrode 418 ineach sequential scan. In another example, in a second scan option 420, afirst scan and a second scan may be performed by overlapping twoelectrodes 422 and 424 in each sequential scan. In one embodiment,additional scans may be performed to increase the resolution of theimage formed by the scans.

FIG. 5 illustrates a method 500 for multi-pattern scanning, according toone embodiment. The processing flow method 500 may be performed byprocessing logic that comprises hardware (e.g., circuitry, dedicatedlogic, programmable logic, microcode, etc.), software (e.g.,instructions run on a processing device to perform hardware simulation),or a combination thereof. Method 500 can provide operations for ananalog frond (e.g., analog front end 220 of FIG. 2). Method 500 may beperformed in any order so as to fit the needs of the functionality to beprovided.

At block 510 of method 500, processing logic concurrently drives a firstset of two or more drive (TX) electrodes of a touch panel of electrodes.In another embodiment, a single TX electrode may be driven at a time. Inone embodiment, to drive the TX electrodes, processing logic may inducea square wave on electrode channels connected to the TX electrodes. Atblock 515, processing logic concurrently drives a second set of two ormore drive (TX) electrodes of the touch panel of electrodes. At block520, processing logic concurrently receives two or more signals (e.g.,two or more first signals) from a first set of two or more sensing (RX)electrodes of the panel of electrodes in response to driving the firstset of two or more TX electrodes concurrently. In another embodiment, asingle signal corresponding to a single RX electrode may be received ata time. At block 525, processing logic concurrently receives two or moresignals (e.g., two or more second signals) from a second set of two ormore sensing (RX) electrodes of the panel of electrodes in response todriving the second set of two or more TX electrodes concurrently.Processing logic at block 530 may then determine a first capacitance fora first unit cell including at least four intersections of the first setof two or more TX electrodes and the first set of two or more RXelectrodes. At block 535, processing logic may determine a secondcapacitance for a second unit cell including at least four intersectionsof the second set of two or more TX electrodes and the second set of twoor more RX electrodes. In one embodiment, the at least fourintersections of the second unit cell include at least two intersectionsof the first unit cell.

Processing logic may continue to concurrently scan additional electrodesof the touch sensing to determine additional capacitance values of unitcells of the touch panel of electrodes. For example, processing logicmay concurrently drive a second set of two or more TX electrodes andconcurrently receive two or more signals (e.g. two or more secondsignals) from a second set of two or more RX electrodes of the panel ofelectrodes in response to driving the second set of two or more TXelectrodes concurrently. In one embodiment, a TX MUX may control theconcurrent selection (e.g., driving) of various TX electrodes and an RXMUX may control the concurrent selection (e.g., sensing) of various RXelectrodes. Processing logic may determine a second capacitance for asecond unit cell comprising at least four intersections of the secondset of two or more TX electrodes and the second set of two or more RXelectrodes.

In a first scan mode, processing logic activates sequential overlappingsets of TX and RX electrodes in each scan (e.g., TX1 and TX2 with RX1and RX2 concurrently, then TX2 and TX3 with RX2 and RX3 concurrently,etc.) so that the first unit cell and the second unit cell include atleast one common intersection (e.g., the TX2 and RX2 intersection. Inthis case, the pitch of the scan (the distance between unit cells), andtherefore the resolution of the scan, may be the same as the resolutionof a scan of each intersection of the touch sensing array. In oneembodiment, the unit cells of consecutive scans do not include anycommon intersections.

In other scan modes, processing logic may activate non-sequential,non-overlapping sets of TX and RX electrodes in each scan (e.g., TX1 andTX2 with RX1 and RX2 concurrently, then TX3 and TX4 with RX3 and RX4concurrently, etc.) so that a second unit cell does not share anyintersections a first unit cell. In this case, the pitch of the scan,and therefore the resolution of the scan, may be the half the resolutionof a scan of each intersection of the touch sensing array. In oneembodiment, the centers of the unit cells may be located on the firstset of TX electrodes or the second set of TX electrodes.

In one embodiment, processing logic may store the first capacitance andthe second capacitance in a memory and process the capacitances todetermine a presence of a ridge or valley of a fingerprint on the touchsensing array. In one embodiment, to detect ridges and valleys, theelectrodes of a touch sensing array may have a pitch of approximately 68microns. In another embodiment, when ridges and valleys may not bedetected, the touch sensing array may have a pitch of approximately 1mm.

In one embodiment, to perform the multi-pattern scan method 500 on atouch panel of electrodes as described above, processing logic mayinitialize a TX electrode index (tx|dx) and an RX electrode index(rx|dx) (e.g., to zero) to define a starting point (starting electrodes)of the scan. Processing logic may set a TX electrode offset value(txOffset) and an RX electrode offset value (rxOffset) that indicate apitch (e.g., resolution) of the scan and connect a first set of sensors(e.g, RX(rx|dx), RX(rx|dx+1). Processing logic may concurrently drive afirst set of TX electrodes (e.g., TX(tx|dx+txOffset) andTX(tx|dx+txOffset+1) and concurrently sense a first set of RX electrodes(e.g., RX(tx|dx+rxOffset) and TX(tx|dx+rxOffset+1), increasing rxOffsetand txOffset after each scan. In one embodiment, processing logic mayend the scan when the last RX or TX electrode of the touch panel ofelectrodes has been scanned (e.g. when rx|dx or tx|dx are equal to orgreater than a threshold).

FIG. 6 illustrates one embodiment of a system 600 that includes a touchdetection circuit similar to that described with regard to FIG. 1. Atouchscreen display 610 may include a display unit, such as an LCD, andsensing electrodes disposed over the surface of the display to detect auser's finger. Display Controller/Driver 614 may be configured tocontrol what is shown on touchscreen display 610. Touch controller 612may be configured detect a user's finger using any commonly used sensingmethod. The output of the touch controller 612 may be communicated to anapplication processor 640, which may also communicate to displaycontroller/driver 614. Touch controller 612 may also be configured toreceive commands and data from application processor 640. Touchcontroller 612 may be configured to communicate with applicationprocessor 640 to provide touch detection functions to system 600.Fingerprint controller 632 may be configured to detect and distinguishfingerprints on fingerprint sensor 630.

FIG. 7 illustrates a method for combining multi-pattern scan images,according to one embodiment. The processing flow method 700 may beperformed by processing logic that comprises hardware (e.g., circuitry,dedicated logic, programmable logic, microcode, etc.), software (e.g.,instructions run on a processing device to perform hardware simulation),or a combination thereof. Method 700 can provide operations for a touchcontroller (e.g., touch controller 612 of FIG. 6), fingerprintcontroller (e.g., fingerprint controller 632 of FIG. 6), processingdevice (e.g., application processor 640 of FIG. 6), etc. Method 700 maybe performed in any order so as to fit the needs of the functionality tobe provided.

At block 710 of method 700, processing logic receives first dataassociated with the first scan (e.g., the first image). In oneembodiment, the first data represents capacitance values for virtualelectrodes scanned during the first scan. At block 720, processing logicreceives second data associated with the second scan (e.g., the secondimage). In one embodiment, the second data represents capacitance valuesfor virtual electrodes scanned during the second scan. In oneembodiment, the first and second data represent two RAW data matricesincluding a signal for each quad-pixel intersection (e.g.,S[(0,1);(1,2)] may represent a signal from the intersection of the(RX0+RX1) and (TX1+TX2) electrodes).

At block 730, processing logic combines the first data (e.g., the firstimage) and the second data (e.g., the second image) to generate acombined image. In one embodiment, to combine the first data and thesecond data (e.g., the first image and the second image) processinglogic may combine the odd TX lines from the first image with the even TXlines from the second image.

In one embodiment, to generate the first image and the second image, RXelectrodes are scanned in overlapping pairs (e.g.,(RX0+RX1)->(RX1+RX2)-> . . . ->(RX101+RX102)->(RX102+RX103)). In oneembodiment, to generate the first image and the second image the TXelectrodes are scanned in non-overlapping pairs. For example, for thefirst image: (TX0+TX1)->(TX2+TX3)-> . . . ->(TX100+TX101)->(TX102+TX103)and for the second image: (TX1+TX2)->(TX3+TX4)-> . . .->(TX101+TX102)->(TX103+TX104). In one embodiment, the second image isgenerated by shifting the starting TX electrode of the first image byone TX electrode (e.g., the second image starts with TX1 and the firstimage starts with TX0).

FIG. 8 illustrates multi-pattern scan images, according to oneembodiment. As described above with respect to FIG. 7, a first image 802and a second image 804 may be combined to generate a combined image 806.In one embodiment, the first image 802 and the second image 804 are theoutput of a first scan and a second scan of overlapping electrodes(e.g., virtual electrodes). The first image 802 and the second image 804may be combined to generate a combined image 806 having the sameresolution of a single pixel scan.

In the above description, numerous details are set forth. It will beapparent, however, to one of ordinary skill in the art having thebenefit of this disclosure, that embodiments of the present inventionmay be practiced without these specific details. In some instances,well-known structures and devices are shown in block diagram form,rather than in detail, in order to avoid obscuring the description.

Some portions of the detailed description are presented in terms ofalgorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here and generally,conceived to be a self-consistent sequence of steps leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared and otherwise manipulated. It has provenconvenient at times, principally for reasons of common usage, to referto these signals as bits, values, elements, symbols, characters, terms,numbers or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as “integrating,” “comparing,” “balancing,” “measuring,”“performing,” “accumulating,” “controlling,” “converting,”“accumulating,” “sampling,” “storing,” “coupling,” “varying,”“buffering,” “applying,” “driving,” “activating,” “receiving,”“determining,” or the like, refer to the actions and processes of acomputing system, or similar electronic computing device, thatmanipulates and transforms data represented as physical (e.g.,electronic) quantities within the computing system's registers andmemories into other data similarly represented as physical quantitieswithin the computing system memories or registers or other suchinformation storage, transmission or display devices.

The words “example” or “exemplary” are used herein to mean serving as anexample, instance or illustration. Any aspect or design described hereinas “example” or “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe words “example” or “exemplary” is intended to present concepts in aconcrete fashion. As used in this application, the term “or” is intendedto mean an inclusive “or” rather than an exclusive “or.” That is, unlessspecified otherwise, or clear from context, “X includes A or B” isintended to mean any of the natural inclusive permutations. That is, ifX includes A; X includes B; or X includes both A and B, then “X includesA or B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Moreover, use of the term “an embodiment” or “one embodiment” or“an implementation” or “one implementation” throughout is not intendedto mean the same embodiment or implementation unless described as such.

Embodiments described herein may also relate to an apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the required purposes, or it may comprise ageneral-purpose computer selectively activated or reconfigured by acomputer program stored in the computer. Such a computer program may bestored in a non-transitory computer-readable storage medium, such as,but not limited to, any type of disk including floppy disks, opticaldisks, CD-ROMs and magnetic-optical disks, read-only memories (ROMs),random access memories (RAMs), EPROMs, EEPROMs, magnetic or opticalcards, flash memory, or any type of media suitable for storingelectronic instructions. The term “computer-readable storage medium”should be taken to include a single medium or multiple media (e.g., acentralized or distributed database and/or associated caches andservers) that store one or more sets of instructions. The term“computer-readable medium” shall also be taken to include any mediumthat is capable of storing, encoding or carrying a set of instructionsfor execution by the machine and that causes the machine to perform anyone or more of the methodologies of the present embodiments. The term“computer-readable storage medium” shall accordingly be taken toinclude, but not be limited to, solid-state memories, optical media,magnetic media, any medium that is capable of storing a set ofinstructions for execution by the machine and that causes the machine toperform any one or more of the methodologies of the present embodiments.

The algorithms and circuits presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will appear from the description below.In addition, the present embodiments are not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the embodiments as described herein.

The above description sets forth numerous specific details such asexamples of specific systems, components, methods and so forth, in orderto provide a good understanding of several embodiments of the presentinvention. It will be apparent to one skilled in the art, however, thatat least some embodiments of the present invention may be practicedwithout these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present invention. Thus, the specific details set forth above aremerely exemplary. Particular implementations may vary from theseexemplary details and still be contemplated to be within the scope ofthe present invention.

It is to be understood that the above description is intended to beillustrative and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A sensing circuit comprising: a first inputoperatively coupled to a first electrode; a first set of two or moreinputs operatively coupled to a first set of two or more electrodes,respectively, forming a first intersection and a second intersectionwith the first electrode; a second set of two or more inputs operativelycoupled to a second set of two or more electrodes, respectively, formingthe second intersection and a third intersection with the firstelectrode; a scan control circuit, operatively coupled to the firstinput, the first set of two or more inputs, and the second set of two ormore inputs, to concurrently select the first set of two or moreelectrodes and to concurrently select the second set of two moreelectrodes via a multiplexer; an analog front end (AFE) configured to:generate a first digital value representative of a first mutualcapacitance of a first unit cell, wherein the first unit cell comprisesthe first intersection and the second intersection; and generate asecond digital value representative of a second mutual capacitance of asecond unit cell, wherein the second unit cell comprises the secondintersection and the third intersection; and a channel engine,operatively coupled to the AFE, configured to generate a firstcapacitance value and a second capacitance value corresponding to thefirst unit cell and the second unit cell, respectively.
 2. The sensingcircuit of claim 1, wherein the first electrode is a drive (TX)electrode and the two or more electrodes of the first set are two ormore sensing (RX) electrodes, and wherein, to concurrently select thefirst set of two or more RX electrodes, the scan control circuit is to:drive a first signal on the TX electrode; and cause the multiplexer toelectrically couple the first set of two or more RX electrodes toconcurrently receive a second signal generated from a current induced onthe first set of two or more RX electrodes in response to the firstsignal.
 3. The sensing circuit of claim 1, wherein the first electrodeis a sensing (RX) electrode and the two or more electrodes of the firstset are two or more drive (TX) electrodes, and wherein, to concurrentlyselect the first set of two or more TX electrodes, the scan controlcircuit is to: cause the multiplexer to electrically couple the firstset of two or more TX electrodes to concurrently drive a first signal onthe two or more TX electrodes; and receive a second signal generatedfrom a current induced on the RX electrode in response to the firstsignal.
 4. The sensing circuit of claim 1, further comprising a secondset of two or more drive (TX) electrodes comprising the first electrode,forming at least four intersections with the first set of two or moreelectrodes, wherein the two or more electrodes of the first set are twoor more sensing (RX) electrodes, and wherein the scan control circuit isfurther to: cause the multiplexer to electrically couple the second setof two or more TX electrodes to concurrently drive a first signal on thetwo or more TX electrodes; and cause the multiplexer to electricallycouple the first set of two or more RX electrodes to concurrentlyreceive a second signal generated from a current induced on the firstset of two or more RX electrodes in response to the first signal.
 5. Thesensing circuit of claim 4, wherein a first number of TX electrodes inthe second set of two or more TX electrodes is different than a secondnumber of RX electrodes in the first set of two or more RX electrodes.6. The sensing circuit of claim 1, wherein the first electrode, thefirst set of two or more electrodes, and the second set of two or moreelectrodes are self-capacitance electrodes.
 7. The sensing circuit ofclaim 1, further comprising a fingerprint controller to detect apresence of a ridge or a valley of a fingerprint on a panel ofelectrodes based on the capacitance value.
 8. A method comprising:concurrently driving, by a processing device, a first set of two or moredrive (TX) electrodes of a touch panel of electrodes; concurrentlydriving a second set of two or more TX electrodes of the touch panel;concurrently receiving two or more first signals from a first set of twoor more sensing (RX) electrodes of the panel of electrodes in responseto driving the first set of two or more TX electrodes concurrently;concurrently receiving two or more second signals from a second set oftwo or more RX electrodes of the panel of electrodes in response todriving the second set of two or more TX electrodes concurrently;determining, by the processing device, a first capacitance for a firstunit cell comprising at least four intersections of the first set of twoor more TX electrodes and the first set of two or more RX electrodes;and determining a second capacitance for a second unit cell comprisingat least four intersections of the second set of two or more TXelectrodes and the second set of two or more RX electrodes, wherein theat least four intersections of the second unit cell comprise at leasttwo intersections of the first unit cell.
 9. The method of claim 8,further comprising: generating a first image based on the firstcapacitance; generating a second image based on the second capacitance;and generating a combined image based on the first image and the secondimage.
 10. The method of claim 9, wherein the combined image comprises:an odd pixel column comprising the first capacitance and an even pixelcolumn comprising the second capacitance.
 11. The method of claim 9,further comprising: storing the first capacitance and the secondcapacitance in a memory; and determining, based on the first capacitanceand the second capacitance, a presence of a ridge or valley of afingerprint on the touch panel of electrodes.
 12. The method of claim 8,wherein the concurrently driving the first set of two or more TXelectrodes of the touch panel of electrodes comprises causing amultiplexer coupled to the two or more TX electrodes to electricallycouple the two or more TX electrodes to concurrently drive a signal onthe two or more TX electrodes.
 13. The method of claim 8, wherein theconcurrently receiving the two or more first signals from the first setof two or more RX electrodes comprises causing a multiplexer coupled tothe two or more RX electrodes to electrically couple the two or more RXelectrodes to concurrently receive the two or more first signals on thetwo or more RX electrodes.
 14. A touch detection system comprising: atouch panel of electrodes comprising: a first electrode disposed alongfirst axis of the touch panel; a first set of two or more electrodesdisposed along a second axis of the touch panel, the first electrode andthe first set of two or more electrodes forming a first intersection anda second intersection with the first electrode; and a second set of twoor more electrodes disposed along the second axis of the touch panel,the first electrode and the second set of two or more electrodes formingthe second intersection and a third intersection with the firstelectrode; a scan control circuit, operatively coupled to the touchpanel of electrodes, to concurrently select the first set of two or moreelectrodes and to concurrently selected the second set of two or moreelectrodes via a multiplexer; an analog front end (AFE) configured to:generate a first digital value representative of a first mutualcapacitance of a first unit cell, wherein the first unit cell comprisesthe first intersection and the second intersection; and generate asecond digital value representative of a second mutual capacitance ofsecond a unit cell, wherein the second unit cell comprises the secondintersection and the third intersection; a channel engine, operativelycoupled to the AFE, configured to generate a first capacitance value anda second capacitance value corresponding to the first unit cell and thesecond unit cell, respectively; and a memory, operatively coupled to theAFE, configured to store the capacitance value generated by the channelengine.
 15. The touch detection system of claim 14, wherein the firstelectrode is a drive (TX) electrode and the two or more electrodes ofthe first set are two or more sensing (RX) electrodes, and wherein toconcurrently select the first set of two or more RX electrodes the scancontrol circuit is to: drive a first signal on the TX electrode; andcause the multiplexer to electrically couple the first set of two ormore RX electrodes to concurrently receive a second signal generatedfrom a current induced on the first set of two or more RX electrodes inresponse to the first signal.
 16. The touch detection system of claim14, wherein the first electrode is a sensing (RX) electrode and the twoor more electrodes of the first set are two or more drive (TX)electrodes, and wherein to concurrently select the first set of two ormore TX electrodes the scan control circuit is to: cause the multiplexerto electrically couple the first set of two or more TX electrodes toconcurrently drive a first signal on the two or more TX electrodes; andreceive a second signal generated from a current induced on the RXelectrode in response to the first signal.
 17. The touch detectionsystem of claim 14, further comprising a second set of two or more drive(TX) electrodes forming at least four intersections with the first setof two or more electrodes, wherein the two or more electrodes of thefirst set are two or more sensing (RX) electrodes, and wherein the scancontrol circuit is further to: cause the multiplexer to electricallycouple the second set of two or more TX electrodes to concurrently drivea first signal on the two or more TX electrodes; and cause themultiplexer to electrically couple the first set of two or more RXelectrodes to concurrently receive a second signal generated from acurrent induced on the first set of two or more RX electrodes inresponse to the first signal.
 18. The touch detection system of claim17, wherein a first number of TX electrodes in the second set of two ormore TX electrodes is different than a second number of RX electrodes inthe first set of two or more RX electrodes.
 19. The touch detectionsystem of claim 17, wherein a first number of TX electrodes in thesecond set of two or more TX electrodes is the same as a second numberof RX electrodes in the first set of two or more RX electrodes.
 20. Thetouch detection system of claim 14, further comprising a fingerprintcontroller to detect a presence of a ridge or a valley of a fingerprinton the touch panel of electrodes based on the capacitance value.